2015 Local Roads Workshop - PowerPoint Presentation

Presentation on theme: "2015 Local Roads Workshop"— Presentation transcript:

Slide1

2015 Local Roads WorkshopGaylordMarch 12, 2015Slide2

Best Practices for HMA ConstructionSlide3

HMA Construction Inspection

Sound inspection practices during construction are vital to obtain quality

Both Agency and Contractor are responsible

Process control and acceptance procedures alone will not ensure quality

Key components of Inspection are:

Enforcement of specifications

Ensure good practices are being used

Observation of materials and workmanshipSlide4

HMA Construction InspectionSlide5

What is Quality?Slide6

Definition of Quality for HMA

How do we define Quality?

Meets Agency mixture specifications

Meets Agency density specifications

Smooth riding surface

Uniform texture and appearance

Obtains expected service life

Long Lasting asphalt pavementSlide7

Responsibilities

Represent the owner’s interests

Keep daily construction diary

Monitor ambient air and mat temperaturesTrack tonnage with truck ticketsCalculate yieldMonitor compaction with nuclear or non-nuclear gaugeObserve materials and workmanshipMake sure that good practices are being used

HMA Construction InspectionSlide8

Usually spelled out in specifications

Checking yield/thickness of materials being placed

Adhering to weather and temperature limitations

Checking mix and mat temperatureAcceptance testing of final density

Routine Duties of InspectorSlide9

MDOT Temperature and Weather Limitations

Min temp 35 deg. F, min. 200

lbs

/sydMin temp 40 deg. F, min. 120 lbs/sydMin temp 50 deg. F, any course

Temperature and Weather LimitationsSlide10

Min. and Max. Mix TemperaturesSlide11

Why does it matter if the mix is too cold?

Because the mix stiffens as it cools. This makes it difficult to obtain proper roadway compaction.

Proper roadway compaction is probably THE most important factor in determining the logevity of the roadway. Every effort must be made to obtain the target density during the compaction process.

Temperature and Weather LimitationsSlide12

What about maximum mix temperature?

Temperature and Weather LimitationsSlide13

Why does it matter if the mix is too hot?

Because the lighter fractions of the asphalt binder evaporate at higher temperatures.

This makes the remaining binder stiffer, and causes early aging of the binder. Aged binder tends to be more brittle, and more suseptable to cracking.

Temperature and Weather LimitationsSlide14

Measuring Density

Density Acceptance

Using cores . . .

or density gaugeSlide15

Watch for Segregation

Truck-end segregation is caused by segregation in the truck transferred to the paver.

Make sure the trucks are being loaded in multiple drops!Slide16

Hauling

Provide a steady flow of material to the paving operation

Deliver mix at consistent and correct temperature

PavingContinuous operation (keep paver moving)CompactionCompact mix when it is hot

Best PracticesSlide17

Surface Prep – Good Practice?Slide18

Poor Tack ApplicationSlide19

Tack Coat

To promote the bond between old and new layers.

To prevent slippage between layers

To provide an additional moisture barrier, especially when applied along transverse

and longitudinal vertical surfaces

Why do we use Tack Coat?

MS-22

5-10Slide20

Tack Coat

SS-1, but also SS-1h, CSS-1, CSS-1h, CRS-2, or straight binder

Clean before applying

Coat surfaces that will contact new HMA

Watch accidental pick-up

Tracking

Do not apply:

In

cold or windy

weather

Or

on wet surfaces with free

water Slide21

Tack Coat

Original emulsion is often diluted at 1:1 ratio

Ehance

sprayability

Apply

at

a rate of 0.05 to 0.15 gal/yd

2

Adjusted based on surface texture

Less

on

smooth

More

on rough)

Make sure tack breaks before paving

Advice:

Don’t allow the tack

too far in advance of paving

Wind blown dust & debris minimizes its effectivenessSlide22

Tack Coat

GOOD

Even uniform coverage

No puddles

No stripes

BAD

Uneven coverage

Clogged nozzles / improper orientation

Stripes are clearly visibleSlide23

Tack Coat

Full width of mat to minimize movement of unsupported edge

Photo Courtesy of Jim

ScherocmanSlide24

HMA Construction Inspection

Sound inspection practices during construction are vital to obtain quality

Both Agency and Contractor are responsible

Process control and acceptance procedures alone will not ensure quality

Key components of Inspection are:

Enforcement of specifications

Ensure good practices are being used

Observation of materials and workmanshipSlide25

Questions?

Best Practices for HMA Construction